Electric clock



9 7 2, 3 9 1 E c m R P E c v May 6, 1924.

ELECTRIC CLOCK Filed Sept. 5, 1923 2 Sheets-Sheet l "m r r rn May a, 19241 1,493,279

C. E. PRINCE ELECTRIC CLOCK Filed Sept. 5, 1923 2 Sheets-Sheet 2 Z liyv'i PRINCE, a subject of the Kin Patented May 6, 1924.

UNITED STATES CHARLES EDMOND PRINCE, OF BURCHETTS GREEN, ENGLAND.

ELECTRIC CLOCK.

Application filed September 5, 1923.

17 '0 all 20710-221 it may concern:

Be it known that I, CHARLES EDMOND of- Great Britain, residing in Burchetts xreen, England, have invented certain new and useful Improvements in Electric Clocks, of which the following is a specification.

This invention relates to electrically driven clocks and the main idea of the invention is the mechanical separation of the pendulum or time-keeping element from the clockwork or indicating mechanism, so that the former vibrates substantially freely, such work as it has to perform being not only very small but also preferably of equal value at each swing of the timekeeping element. The time-keeping properties of the oscillating time-keeping element are thus entirely unaffectedby lack of accuracy in the construction or adjustment of the indicating or clock mechanism which can therefore be of a comparatively rough and cheap character without detriment to the accuracyof its indications.

The time indicating .mechanism may be of any suitable known character the step by step movements of which are either effected or controlled by the operation of an electromagnetic device which is included in a circuit controlled by the swings of the pendulum and is momentarily closed at each swing by the engagement of a light yielding contact, and is automatically openedby an auxiliary device, such as an electromagnetic circuit breaker, prior to the disengagement of the pendulum contact. The circuit arrangements are such that upon each swing of the pendulum a transient current traverses the circuit energizing the relay or electromagnet which controls or actuates the indicating mechanism, and also traverses the energizing coil or coils of the circuit breaker. which thereupon breaks the circuit and effects other connections such that, upon the re-establishment of the current on the next swing of the pendulum, this current traverses the energizing coil or coils of the circuit breaker in the reverse direction.

The impulses required to maintain the amplitude of the pendulum swings may be derived from the transient currents in the pendulum controlled circuit, for example by means of a solenoid or electromagnet traversed by such currents and exerting a pull on a soft iron bar rigid with the pendulum, or these currents may be utilized alternately Serial No. 881,084.

to energize and release a gravitational or spring device through which an impulse is periodically applied to the pendulum. or any other suitable means may be adopted for automatically sustainingtlie pendulum vibrations, and such means may alternatively be operated by currents in a circuit established periodically by a contact or contacts upon or controlled by any suitable moving part of the time indicating mechanism.

In the accompanying drawings Fig. 1 is an elevation, more or less diagrammatical. of an electrically driven clock illustrating one arrangement for carrying the invention into practice; Fig. 1 a detail showing the preferred suspension for the pendulum; Fig. 2 is a diagram of the electric circuits: Fig. 3 a detail illustrating one form of spring contact; and Fig. 4 an alternative arrangement of the automatic circuit breaker: Fig. 5 is a diagram similar to Fig. 2- but showing a different arrangement of circuit breaker; and Figs. 6 and 7 are diagrammatic -views of further modifications.

Referring first to Fig. 2, the pendulum or timing element 1. which is pivoted at 2, carries a pair of light contact springs 3, 4 one on either side of the pendulum, which cooperates with fixed contacts 3', 4. These fixed contacts 3, 4' are permanently con nected by leads 5, 6 with two fixed contacts 7 and 8 res ectively of the movable element 9 of an e ectromagnetic circuit reverscr. The contact 7 is a member of a pair of contacts 7 7 which cooperate with a spring contact 10 of the movable element, and the contact 8 is one of a pair of contacts 8 and 8 which cooperate with another spring contact 11 of the movable element. The contacts 7', 8' are connected by leads 12 and 12" respectively and lead 12 with one pole of a battery 13, the other pole of which is connected by leads 14', 14 with the pendulum through its suspension at 2. The leads 14', 14 include an electromagnetic device indicated by the coil 15 which is adapted to operate or control the time indicating device indicated by 16.

The movable element 9, which comprises an energizing coil and a soft iron core, oscillates upon a central pivot 9 under the influence of a permanent magnet 9, according to the direction of the current. in the energizing coil, so that in one position the fixed contact 7 is electrically connected through the flexed spring contact 10, coil 9 and flexed to be swinging towards t e left, then when contact 3 engages the contact 3' a circuit is established from battery 13 through leads 12, 12", contacts 8', 11, coil 9, contacts 10, 7,

lead 5, contacts 3', 3, lead 14, electromagnet 15, lead 14 back to battery 13. :VVhen the current flows in the direction just explained, the polarity of the ends of the movable element 9 becomes North, so that the movable element 9 is, under the influence of the fixed magnet 9', turned about its pivot 9 by the momentum required before the flexed springs 10 and 11 break contact with the fixed contacts 7 and 8, respectively. The springs 10 and 11 are then moved into contact with the fixed contacts 7' and 8, respectively. When the springs 10 and 11 move into this new position the circuit is broken and the duration of engagement between contacts 3 and 3' is arranged to be such that the circuit is broken at the contacts 7, 10 before it is broken at the contacts 3, 3' when the pendulum 1 swings in the reverse direction. As the pendulum swings from left to right, contact is established between the contacts 4, 4 thereby completing the circuit from battery 13 through leads 12, 12', contacts 7 and 10, coil 9, contacts 11, 8, lead 6, contacts 4, 4, lead 14, electromagnetic coil 15, lead 14' back to battery.' The current thus established again reverses the polarity of the movable element 9 to make the ends thereof South, so that the movable element 9 is again turned upon its pivot into the other operative position. There is therefore a transient current through the device 15 upon each swing of the pendulum, and it is to be noted that the circuit traversed by this current is not broken at the pendulum con-.

tacts 3, 4 butjat the circuit breaker contacts 10 and 11. Each transient current energizes the device 15 whichis arranged, upon being energized, to operate the clock indicating mechanism 16 or alternatively to permit the operation of this mechanism, which is of any suitable known step by step character.

QThere is shown included in the lead 6 a solenoid 17 which is traversed I by the transient current which flows around the circuit when the contacts 4, 4' are 1n engagement, and rigidly attached to the pendulum 1 is an arm 17 .of magnetic vi'material or partly magnetic material suitably arranged with respect to the solenoid 17 so as to come within its influence during art of the swing towards the right and there y receive an impulse which maintains the amplitude of swing of the pendulum.- Any suitable magnetic means may be employed to prevent the action of the coil 17 from producing an increasing amnhtude of swing, as for example by having only the outer end of the rod 17' I of magnetic material or by so grading the cross section or magnetic permeability of the that as soon as the pendulum swings outwardly to the required extent the pull exerted by the coil 17 will be reversed. Coil 17 may be arran ed to impart the sustaining impulse at t e most effective moment, that is when the pendulum has maximum Velocity, or it may be arranged to efl'ect the impulse after that" position has been passed,

in which case a sh htly greater energy is required, but this isposltion of the coil tends to compensate automatically for decreasing or increasing am'plitudes of swing.

The arran ement illustrated diagrammatically in ig. 2 is shown in somewhat greater detail in Fig. 1, in which corresponding parts are indicated by the same reference numerals. As shown in this figure the pendulum 1 is suspended by means of a strip 18 of steel or other suitable resilient material rigidly held b a clamp 19 between the jaws between whic 1 the strip 18 passes to an adjustment pin 20. The end of the strip is secured to the adjustment pin 20 which can be raised or lowered in a guide 21 carried by a bracket 22 by means of a nut 23 upon the screwdzhreaded upper end of the pin 20, the clamp 19 being released when such adjustment is effected.

Instead of the pendulum contacts 3, 4 being flexible and the fixed contacts 3', 4', being rigid, the arrangement may be reversed, in which case the yielding fixed contacts may conveniently be of the form shown in Fig. 3. As therein shown, a metal tube 24 closed at its outer end fits friction-tight upon a split boss 25 of a terminal block 26 suitably connected in the circuit. Inside the tube 24 is a hairpin shaped wire sprin 27 the outer free end of which is expose through a cut away portion 24 of the tube 24, while the inner fixed end of thmspring 27 is rigidly connected with the metal tube 24. A certain ran e ofadjustment is possible by rotating t e tubes 24 upon their sockets, or alternatively the contacts 3', 4, whether these are rigid, or yielding, ma be mounted as shown in Fig. '1 on cran arms 28 fulcrumed upon pins 29 suitably connected with the circuit and adjustable by means of handles 30, suitable means such as the pin and slot clamps 31 being provided to secure the contacts after adjustment.

In the arrangement shown in Figs. 1 and 2the movable element 9 of the circuit breaker is non-polarized and the fixed element 9' is polarized. In the modification shown in Fig. 4 the movable element 9 is polarized as by means of a permanent magnet 9", while the fixed element 9' consisting of a horseshoeelectromagnet having an energizing coil on each limb and a soft iron core is non-polarized and the circuit arrangements are modified so that the polarity of the horseshoe magnet is changed by the our rent traversing one of the energizing coils at one swing of the pendulum and the other energizing coil upon the reverse swing.

In the further modification shown in Fig. 5 the movable element 9 is polarized by nieans of a permanent magnet 9 and carries an arm having a. flexible contact memher 10 which swings between two fixed contacts 10, 10 energizing coils on the two elements of a. soft iron core 9. In either position of rest the flexible contact 10 is flexed to the extent necessary to give appropriate duration to the fleeting impulse current.

The rate of the clock is conveniently adjusted by means of the pendulum adjustment hereinbefore described, and the error may also conveniently be corrected, e. g. upon receipt of a correct time signal from any source. Thus, if the clock is too fast the indicating mechanism 16 may be temporarily cut out by a short circuiting lead 32 shown by the dotted and dashed line in Figs. 1 and 2, which is connected across the terminals of the recording mechanism as required by means of a switch such as indicated at 33 in Fig. 1. When this circuit is closed the recording mechanism stops and upon releasing the push button when. the time as recorded by the clock coincides with the correct time the recording mechanism resumes functioning. Similarly by connecting the contacts 3", 4' with the pendulum suspension, as indicated by the dot and dashed lines 34, 35 in Fig. 2, which connection'may be effected as by means of a switch 36 indicated in Fig. 1, the automatic circuit breaker 9 will work rapidly and so advance the hands of the time recording mechanism quickly to correct the error of a. slow running clock, the push switch being released when the recording mechanism again indicates the true time.

It is to be noted that the duration of the transient current which operates the recording mechanism depends merely upon the time constant of the automatic circuit breaker 9 so long as the duration of-contact of the pendulum contacts 3, 3' and 4, 4 is not less than the time lag of the circuit breaker. Consequently theclock will work perfectly with quite a small amplitude of swing and therefore with exceptionally small air resistance and circular error.

Further, the sustaining impulse applied to the pendulum tends to be self-correcting for variations of the E. M. F. of the battery. The contacts of the circuit breaker do not open instantaneously when a current is established through it, since the contacts are flexible, so that should the E. M. F. of the battery decrease and with it the connected respectively with energizing current of the contact breaker and of the sustaining solenoid 17 the weaker current will be maintained -for a longer period, thereby tending to give a constant sustaining impulse to the pendulum.

A art from overcoming air resistance the wor done by the pendulum is limited to the bending or compression of the light s rings 3 and 4- on each excursion of the pen ulum, this Work being stored in the springs as potential energy which is returned to the pendulum upon its return swing, and even should the work involved in compressing these springs not be perfectly constant, consequent for example upon change in the elasticity of the springs, the period of the endulum would not be affected by such 0 ange.

As these pendulum contacts come into place only in the establishment of the circuit and never break the circuit and as, moreover, they are of the nature of rubbing contacts, there is no sparking at these contacts nor any tendency for them to become dirty or stick together. The extremely small loss in friction at these rubbing contacts is equivalent only to a minute addition to the air resistance of the pendulum, but unlike the air resistance it is independent of such variables as barometric pressure and, being constant, does not affect the time kee ing, but only and to quite an inconsidera le extent the amount of energy required to sustain the pendulum vibrations.

It will be readily understood that the invention may be applied either to a self-contained electrically driven clock or one or more clocks may be driven from a distance from a pendulum and circuit breakin apparatus such as hereinbefore described p aced in a position in which it is free from dlsturbance, or by means of a master clock operating according to the present invention. Thus, for example, as shown in Fig. 7, in place of the clock mechanism 16 there may be substituted a relay 9 controlling a local circuit, including a battery) 13, by means of which one or more step y step clocks 16 of any size can be operated.

In the modified arrangement illustrated in Fig. 6 the circuit 5 operating the sustaining solenoid 17 and the clock mechanism 16- is controlled by contacts 40, 41, one of which is fixed and the other is movable, while subject to a centerin or positioning device such as, for examp e, a spring 42, which bears u on an arm 43 of the pivoted contact 41. T is arm 43 is in the path of a pin 44 carried by the pendulum 1, and the arrangement is such that upon the pendulum swin ing in one direction, e. g. from left to rig t, the arm 43 is displaced a ainst the return action of spring 42 so as to ring contacts 41, 40 into electrical engagement, the centerin .device restoring the arm 43 to its norma position ready for engagement with pin 44 upon the next succeeding swing of the pendulum in the same direction. The transient current thereby established in circuit 5 serves to operate the time indicating mechanism indicated at 16 by any usual electromagnetic device and also to energize the sustaining solenoid 17 Having thus described the nature of the said invention and the best means I lmow of carrying the same into practical efiect, I claim 1. In an electrically driven clock, a timeindicating mechanism and an oscillating time-keepin element of which the oscillations are su stantially free from the timeindicating mechanism, an electromagnetic device controlling the operation of the timeindicating mechanism, a pair of make-andbreak devices in the electric circuit to said electroma etic device alternately opened and close .by the oscillating movement of the time-keeping element, and an auxiliary device for breaking said circuit.

2. An electrically-driven clock according to claim 1 wherein the auxiliary device for breaking the circuit to the electromagnetic device comprises a polarized element and a nonpolarized element, the latter of which is ener ized by the current in the circuit contro ed by the time-keepin element.

3. An electrically-driven c ock according to claim 1 wherein the auxiliary device for breaking the circuit to the electromagnetic device comprises a non-polarized element in'said circuit and-a polarized element, one of which elements is movable, said movable element adapted, when the nonpolarized element is energized by the 010s of one or the other of said make-and-bri a fi devices, to change its position to first break the energizing circuit to the electromagnetic device and then to establish connection to the other make and break device, whereby on the next oscillation of the time-keepin elementthe circuit thereby closed to sai non-polarized element reverses the polarity of the latter.

4. An electrically driven clock according to claim 1, wherein means are. provided for rendering the time-indicating mechanism inoperative while the time-keeping element continues to function.

5.. An electrically driven clock according to claim 1, wherein means are provided for electrically operating the time-indicating mechanism independently of the time-keeping element. i

6. An electrically driven clock according to claim 1, wherein the time-indicating mechanism is operated by the current in a local circuit controlled by the time-keeping element.

7. In an electrically driven clock according claim 1, means for imparting periodic sustaining impulses to the timekee in ele ment by means of. currents in the circuit established by the time-keeping element.

8. In an electrically-driven clock accord I ing to claim 1, means for imparting sustaining impulses to the time-keeping element by means of currents in the circuit established by the time-keeping element, the frequency of which sustaini impulses is controlled by the time-indicating mechanism.

9. An electrically driven clock according to claim 1, wherein the time-keeping element is a pendulum and the make-and-break de vices comprise two 'fixed contacts one on either side of the pendulum, and a pair of contacts carried by said pendulum and cooperating with said fixed contacts respectively, one of each cooperating pair of (-on tacts being of the character of a light spring.

10. An electrically-driven clock according to claim 1, wherein the time-keeping element comprises a pendulum and the make-andbreak devices comprise a pair of contacts, one on each side of the pendulum, and a second pair of contacts carried by said pendulum and cooperating, respectively, with said first-named contacts, one contact of each cooperating pair being adjustable in position for varying the moment of contact with its cooperatin element.

11. An e ectrically-driven clock according to claim 1, wherein the time-keeping element com rises a pendulum and the pair of makeandreak'devices are located, respectively, on opposite sides of said pendulum, each of said make-and-break devices comprising a normally fixed contact and a contact carried by said pendulum, a pair of crank levers ad-' justable in position by rotation about their fulcrums and each carrying one of said fixed contacts, and means for clamping said crank levers in adjusted position. V

12. An electrically-driven clock according to claim 1, wherein the time-keeping element comprises a endulum and the pair of make-and-break evices each comprises a contact carried by said pendulum and a contact with which said first-named contact, co operates, said last-named contacts each being mounted to swing in an are for adjustment toward and away from said pendulum.

13. An electrically-driven clock according to claim 1, wherein the auxiliary device for breaking the circuit to the electromagnetic device com rises a movable magnetic element, a spring contact carried by said movable element, and a pair of adjustable but normally fixed contacts with which said spring contact coo crates.

In testimony w ereof I'have signed my name to this specification.

CHARLES EDMOND PRINCE. 

